1. Field of the Invention
The present invention relates to a drive motor for a recording disk for driving various kinds of recording disks such as CD, DVD, PD, or the like and a recording disk drive using the drive motor for a recording disk.
2. Background Art
For example, as a drive motor for a recording disk, a structure shown in FIG. 11 has been known. A rotor 100 of the motor includes a shaft 104 rotatably supported to a sleeve 102 which is a static member, a rotor holder 106 supported at an axially upper portion of the shaft 104, and a disk holder 108 supported above the rotor holder 106 at the axially upper side of the shaft 104. The disk holder 108 includes a turn table 115 on which a recording disk 114 is mounted, a centering portion portion 116 provided in the central portion of the turn table 115, and a plurality of chucks 112 radially outwardly biased by respective coil springs 110 circumferentially evenly disposed in the centering portion portion 116.
When such a motor is used, a central hole of the recording disk 114 is attached to the centering portion portion 116. When the centering portion portion 116 begins fitting into the central hole of the recording disk 114, each of the chucks 112 is pushed by an inner circumferential surface of the central hole of the recording disk 114 to move radially inwardly. Then, when the recording disk 114 is completely attached and is mounted on a disk mount surface 115a of the turn table 115, a tip portion 112b of the chuck 112 is pushed by a restoring force of the coil springs 110 to press an upper edge portion of the inner circumferential surface of the recording disk 114, thereby permitting the recording disk 114 to be held on the rotor 100. Consequently, during rotation of the rotor 100, the recording disk 114 neither comes away nor inclines due to a centrifugal force or its own weight.
In the aforementioned structure, since an axial thickness of the recording disk 114 is specified in the standards, a certain axial distance needs to be maintained between the disk mount surface 115a and the tip portion 112b of the chuck 112 in order to hold the recording disk 114.
Therefore, in a state that the tip portion 112b of the chuck 112 is engaged with an upper edge portion of the inner circumferential surface of the recording disk 114 (a state of holding the recording disk), a comparatively large interspace 120 intervenes between a base portion 112a of the chuck 112 and an upper surface of the rotor holder 106.
If the interspace 120 intervenes, when the recording disk 114 is removed from the state that the recording disk 114 is held by the rotor 100, a force (hereinafter, such a force is referred to as a recording disk draw force) required to remove the recording disk 114 from the rotor 100 may be lowered. That is, when the recording disk 114 is removed from the rotor 100, the chuck 112 is pushed by the inner circumferential surface of the recording disk 114 to receive an axially upward force; but, since the interspace 120 intervenes, the chuck 112 easily rotates in the state being biased by the coil springs 110 instead of moving the base portion 112a radially inwardly against the bias of the coil spring 110. Therefore, an axially upward movement amount of the tip portion 112b of the chuck 112 increases, so that the recording disk draw force is remarkably reduced. When the recording disk draw force is reduced, the recording disk 114 may easily come off from the rotor 100 during rotation of the motor due to centrifugal forces, outside shocks, or the like.
Here, an axial size of the interspace 120 can be decreased by reducing the axial thickness of the turn table 115 to move the disk mount surface 115a axially downwardly. However, such a configuration causes rigidity of the turn table 115 to be lowered.
On the other hand, when the spring force of the coil spring 110 is strengthened, that is, when the spring constant is increased, a lowering of the recording disk draw force can be prevented. However, radially inward movement of the chuck 112 becomes difficult, and a force required to mount the recording disk 114 on the rotor 100 (hereinafter, such a force is referred to as a recording disk attachment force) increases. Consequently, attachment of the recording disk 114 to the rotor 100 becomes difficult, resulting in degradation of operability.